1. Field of the Invention
The present invention is directed to a wire technique of a semiconductor device, and more particularly to a measuring-pattern for a width of the wire and a method for measuring the width of the wire using the measuring-pattern.
2. Description of the Related Art
A process for a semiconductor should be performed with high accuracy, so after each step of the process, the manufactured should be subject to a test or an evaluation. Since a width of a wire, among many elements for a semiconductor device is one of significant factors affecting performance and stability of the semiconductor device, we must test as to whether or not the width of a manufactured wire is the same as that of a designed wire.
There are many types of measuring method for the width of wire. Among them, one approach is to directly measure the width of wire using SEM(Scanning Electron Microscope) and another approach is to use a resistance of the wire subjected to a measurement and a resistivity of a material constituting the wire wherein the resistance is determined through a four-probe test. The method using the SEM is to scan the pattern to be measured through accelerated electrons, to magnify the pattern using information contained in secondary electrons generated by the accelerated electrons and then to measure the width of the wire. However, when a sectional view of the pattern is not at a right angle, the width of the wire can not be accurately measured by the SEM. The volume of SEM is great, so a space for the SEM in a production line is large. Also, a cost for the SEM is much.
A technique for measuring the width W1 of wire 10 whose thickness is t1 will be described with reference to FIG. 1. On the wire 10 are arranged four probes p1, p2, p3 and p4 each separated by constant interval S1. The outer two probes p1 and p4 are connected to a power source 11 and the inner two probes p2 and p3 are connected to a voltmeter 12. When the current I from the power source 11 flows through the wire 10, a voltage between the probe p2 and the probe p3 is measured at the voltmeter 12. The resistance of the wire is calculated from the measured voltage using Ohm's law and then the width of the wire is computed by entering the calculated resistance to the following equation. EQU W1=(.rho.*S1)/(R*t1),
wherein .rho. is resistivity of the wire 10. That is, the resistivity of the wire 10 should be previously perceived in order to determine the width of the wire W1. For taking the gauge of resistivity, first a portion of the wire is defined in rectangular form of l1.times.l2 and then four probes are disposed at four corners of the defined rectangular, resepctively. One pair of probes with l2 interval are connected to a power source and the other pair of probes with l2 interval are connected to a voltmeter. The current I flows from the power source to the defined wire, and then a voltage V between the probes is measured at the voltmeter. Thereafter, the resistivity is calculated using Van der Pauw method. In detail, the resistivity is determined by the following equation. EQU .rho.=(V/I)f(l1/l2),
where f(l1/l2) is a correction factor, approximate value determined as a function of average probe separation and average specimen diameter.
Since the approximate value is used in calculating the resistivity, a deviation of the resistivity is possibly apt to be large. In particular, where l1 or l2 is not enough larger than the thickness of the wire measured and the size of the probe, the deviation of the resistivity becomes enormously large. Accordingly, such resistivity inevitably results in a debasement in a measuring reliability of the width of the wire.